The present invention relates to apparatus for producing light pulses and to apparatus and methods using light for cosmetic or therapeutic photo-treatment.
Apparatus of this type may be used for therapeutic purposes including treatment for psoriasis, vascular traumas, telangiectasis, capillary hemangioma, cancerous cells, port-wine stains, and birthmarks and also for depilation.
WO 091/15264 describes a device for treatment of undesired skin disfigurements, which apparatus comprises a gas filled lamp and an optical filter. The lamp is powered by a capacitor charged to about 2,000 volts, which is sufficient for generating a pulse with a pulse duration between ½ and 1 ms.
EP 0 565 331 A2 describes a therapeutic treatment device which includes a gas filled flash lamp and a set of optical filters. The power circuit includes three different pulse forming networks, which may be triggered selectively or successively. Each pulse forming network includes a capacitance and an inductance and a relay contact to trigger the discharge. The three networks are designed for providing different pulse widths. The capacitors are charged to a voltage, typically in the range of from 500 volts to 5 kilovolts.
EP 0 736 308 A2 discloses a method and an apparatus for depilation, wherein an apparatus of a similar kind is used. According to this publication an energy fluence in the order of from 10 to 100 J/cm2 is used for the purpose of killing hair follicles without burning the surrounding skin. The publication also suggests the use of an optically transparent water-based gel applied to the skin prior to treatment and serving the purpose of providing a heat sink to prevent hyperthermia in the skin.
We have found several limitations and problems in devices and methods according to the prior art. Damage to the skin or burns occur very easily, making it difficult to find an energy level at which the pulses will be effective but will not harm the skin. Further the amount of heat absorbed in the optical filters may be excessive, frequently leading to destruction of the filters.
These problems are addressed by the various aspects of the invention set out below which may be used separately or in any combination.